2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/155680We describe two ways to construct finite rational morphisms between fiber products of rational elliptic surfaces with section and some Calabi--Yau manifolds. We use them to construct correspondences between such fiber products that admit at most five singular fibers and rigid Calabi--Yau threefolds.11 pagesAlgebraic Geometry14J32;14J27,14G35text